1. Field of Invention
The present invention relates to an optical thin sheet used for a backlight element assembled within a liquid crystal display (LCD), which has an optical property of high diffusion, such that the light transmitted there-through is uniformly distributed, thereby achieving a desired optical effect.
2. Description of the Prior Art
Since a liquid crystal panel cannot emit light by itself, a back light acting as a light source is an important element for the displaying function of a LCD and is very important for enhancing the luminance of the LCD.
Moreover, the LCD product has been expanded from LCDs in laptop computers or LCD screens to LCD TVs. Thus, critical factors to be considered are sufficient imaging luminance, broad viewing angle, sharp image contrast, and desired service life. In order to meet the requirements, a direct type backlight has become the mainstream technology used in large LCD TVs. FIG. 1 is a schematic view of a direct type backlight module. Referring to FIG. 1, the direct type backlight module comprises a reflecting film (11), a cold cathode fluorescent lamp (12), a diffuser (13), a diffusion film (14), and a brightness enhancing film (15) sequentially from bottom to top.
Though the direct type backlight module product usually provides a high luminance, bright and dark stripes easily occur due to the increase in the number of the lamps, and thereby the uniformity of light is influenced. Thus, a diffuser must be added when designing the backlight module. The diffuser, with a thickness of about 2 mm, is usually composed of polycarbonate (PC) resin or polymethyl methacrylate (PMMA) resin containing organic or inorganic particles, and has a main function of utilizing the particles to allow the light to be refracted and dispersed when passing through two mediums with different refraction indexes, and to distribute the line light emitted from the light source into a plane light, that is, the light coming from a bottom light source is diffused when transmitting through the diffuser and is uniformly dispersed, and then emitted from a front surface.
Although a flat panel liquid crystal display (LCD) is generally required to be light, thin, short, and small, the diffuser is thick and heavy and the material used in the diffuser will absorb light inevitably, thereby wasting a portion of the light. Thus, the light source cannot be used effectively. Moreover, the manufacturing process of the diffuser is time consuming and involves a relatively high manufacturing cost, which is disadvantageous to the module design.
In order to solve the above problem, through a thorough research, the inventors of the present invention found that, an optical thin sheet with an optical property of high diffusion can be used to replace the diffuser currently used in the backlight module for uniformizing light so as to achieve a uniformity effect, and the optical thin sheet has the advantages of being thin and light, and being able to be produced by a simple process at a high yield, which effectively solve the above problem.